Glossary

Mercury

Mercury is the closest planet to the sun and has been known since ancient times. It takes Mercury 88 days to orbit the sun once. Mercury is about 2.5 times smaller than the Earth and is about 28 times less massive. Daytime temperatures on Mercury can get as high as 430°C (800°F)!

Mercury is also the Roman name for Hermes, the son of Zeus and Maia (the daughter of Atlas). Swift Mercury was the herald and messenger of the gods. He carries a messenger's wand (the caduceus) and wears a traveler's cap. He has wings on his ankles, shoulders and cap.